The purpose of this research project is to investigate the role of intramolecular and intermolecular structure in the coupling of electron and proton translocation to ATP synthesis in biological membranes. Through a determination of the overall shapes of relevant membrane molecular components at moderate resolution and of their positions (including the positions of their redox centers) relative to each other and to the overall membrane structure, it is expected that substantial insight will be gained concerning the possible mechanisms of electron and proton translocation and of energy coupling. The techniques of non- resonance and resonance X-ray and neutron diffraction, EXAFS (Extended X-ray Absorption Fine Structure) spectroscopy, optical linear dichroism, three-dimensional electron microscopic image reconstruction, and FRAP (Fluorescence Recovery After Photobleaching) will be utilized to study the relevant membrane proteins including photosynthetic reaction centers, cytochrome oxidase, cytochrome c and cytochrome b/c1 and various complexes thereof primarily in the form of single, oriented monolayer membrane systems and in some instances oriented membrane multilayer systems. The reaction center-cytochrome b/c1-cytochrome c complexes exhibit an efficient light-driven cyclic series of electron transfer reactions.